Safety cap for a liquid reservoir for a motor vehicle

ABSTRACT

A safety cap ( 10 ), for a motor vehicle fluid reservoir ( 14 ), is configured to be attached and fixed to a neck ( 12 ) of the reservoir. The cap includes a screwing cover ( 16 ) with a first screw thread ( 16   ba ), and a safety cell ( 18 ) configured to allow passage of gas between the interior and the exterior of the reservoir, when the cap is fixed to the neck and when a pressure difference between the interior and the exterior of the reservoir is greater or less than at least one predetermined threshold value. The cap includes a ring ( 20 ) with structure ( 30, 30   a,    32 ) for fixing to the neck and a second screw thread ( 22 ) to cooperate with the first screw thread. The cell is at least partly housed in the neck and surrounded by the cover and/or the ring when the cap is fixed on the neck.

TECHNICAL FIELD

The invention relates to a safety cap for a liquid reservoir, in particular for a motor vehicle, the reservoir being, for example, a motor vehicle radiator expansion vessel.

BACKGROUND

Patent document FR-A1-2 646 405 is representative of a known safety cap or valve cap.

A safety cap or valve cap of the type described in that document comprises a cell or valve housing a first valve shutter held in the bottom of the cell using a spring. The upper end of the spring comes into abutment against a fixed element in order thus to allow the valve shutter to move vertically in the event of an overpressure inside the reservoir, until the internal pressure returns to normal. Also arranged inside the cell is a second valve shutter which deforms or is moved by the compression of another spring, in the event of a depression in the reservoir, making it possible to reestablish the lack of pressure.

This safety cap therefore makes it possible, in the event of a depression or an overpressure, to be able to return the cooling circuit to the operating pressure prescribed by the manufacturer. At the present time, overpressure safety conditions are of the order of 1.4 bar, which means that the safety cell operates only for pressures above these limits. In terms of depression, the value needs to be as low as possible, currently 25 mbar. The opening brought about by the movement of each valve shutter is achieved through the inherent elasticity of the associated spring which compresses as soon as the pressure in the circuit reaches the critical conditions imposed by the manufacturer.

In the current state of the art, the safety cap is either screwed onto a neck of the reservoir or fixed to this neck by a bayonet effect.

Bayonet fastening has the advantage of being quick to employ. However, the valve shutter spring is generally used for sealing the reservoir closed, and this reduces the precision of the valve and imposes dimensional and mechanical constrains on the equipment housing it. This disadvantage can be avoided by using a two-spring valve, as mentioned in the foregoing, but that leads to a significant increase in the cost of the cap.

Screw-fastening does not exhibit these disadvantages but takes longer to achieve (several turns of the cap are needed as compared with just a portion of a turn in the case of a bayonet fastening), and this constitutes a disadvantage on an assembly line.

Furthermore, the two current types of fastening have the same fault (which is, however, more critical in the case of the screw-fastened solution). When the cap opens, it is desirable for the flow of often boiling liquid to be directed toward the ground through a duct. This duct is often tricky to produce using current technology.

The present invention proposes a solution to at least some of these problems which is simple, effective and economical.

SUMMARY

The invention thus proposes a safety cap for a fluid reservoir, in particular for a motor vehicle, said cap being configured to be attached and fixed to a neck of said reservoir, said cap comprising:

-   -   a screwing cover comprising a first screw thread, and     -   a safety cell configured to allow the passage of gas from the         interior to the exterior of the reservoir, and/or vice versa,         when the cap is fixed to said neck and when a pressure         difference between the interior and the exterior of the         reservoir is greater or greater than at least one predetermined         threshold value,         characterized in that it additionally comprises:     -   a ring comprising means for fixing to said neck and a second         screw thread configured to cooperate with said first screw         thread, said cell being at least partly housed in the neck and         surrounded by said cover and/or said ring when the cap is fixed         on said neck, and in that said ring comprises an inner annular         surface intended to surround, with clearance, an outer annular         surface of said neck so as to define a space for the passage of         gas between the ring and the neck.

The cap thus offers the advantages of the earlier techniques, without their disadvantages. A motor manufacturer can fix the cap to the reservoir quickly using the means for fixing the ring to the neck of the reservoir. The removal and refitting of the cap by a user wishing for example to add fluid to the reservoir can be performed by unscrewing the cap and screwing it back on.

The cap according to the invention may comprise one or more of the following features, considered in isolation from one another or in combination with one another:

-   -   said ring comprises ribs projecting from said inner surface and         able to cooperate by bearing and/or sliding with said outer         surface of said neck,     -   said ring comprises means for fixing to said neck by bayonet         effect and/or elastic snap-fastening,     -   said ring comprises inner annular rim sectors which are intended         to cooperate by bayonet effect with outer annular rim sectors of         said neck,     -   said sectors of said ring bear first elastic snap-fastening         means intended to cooperate with complementary elastic         snap-fastening means of said sectors of said neck,     -   said ring comprises circumferential through-slots extending         along and in proximity to said sectors so as to provide them         with a certain degree of flexibility,         -   said second screw thread is an external screw thread,         -   said ring comprises second elastic snap-fastening means or             means of determining a hard point, which are configured to             collaborate with complementary means of said cover, at the             end of the screwing-on thereof,         -   the cap additionally comprises an annular seal mounted             around said cell and intended to cooperate with an inner             annular surface of said neck,         -   said cell is borne by said cover,         -   the cap additionally comprises a split ring an inner             periphery of which is engaged in an outer annular groove of             said cell and an outer periphery of which is engaged in an             inner annular groove of said cover,     -   said ring comprises slideways configured to cooperate with rails         of said neck in order to produce guiding by axial sliding when         mounting said ring on said neck,     -   at least one of said slideways bears first elastic         snap-fastening means intended to cooperate with complementary         elastic snap-fastening means of at least one of said rails.

The present invention also relates to a fluid reservoir, in particular for a motor vehicle, said reservoir comprising a neck on which there is intended to be attached and fixed a cap as described hereinabove. Said neck may comprise a cylindrical wall comprising outer annular rim sectors which are intended to cooperate by bayonet effect with inner annular rim sectors of said cap.

The reservoir according to the invention may comprise one or more of the following features, considered in isolation from one another or in combination with one another:

-   -   said sectors of said cylindrical wall bear elastic         snap-fastening means intended to cooperate with first         complementary elastic snap-fastening means of said sectors of         said cap,     -   said cylindrical wall comprises a crenellated free annular edge         comprising solid parts alternating with recessed parts for the         passage of gas,     -   said neck comprises an annular shoulder for the axial bearing of         said cap and onto which a gas passage orifice can open,     -   the reservoir comprises a gas passage duct defining said orifice         and extending substantially over the height of said reservoir,     -   said neck comprises a cylindrical wall and an annular row of         rails projecting from an outer cylindrical surface of this         cylindrical wall, said rails being substantially parallel to one         another and to an axis of revolution of this cylindrical wall,     -   at least some of said rails bear elastic snap-fastening means         intended to cooperate with first complementary elastic         snap-fastening means of said cap.

The present invention also relates to an assembly comprising a reservoir and a cap both as described hereinabove, said cap being:

-   -   either premounted on said neck, said cap being held on said neck         only by the cooperation between an annular seal and a         cylindrical wall of said neck,     -   or fixed to said neck by bayonet effect and/or elastic         snap-fastening.

Said recessed parts of said neck may be in fluidic communication with said space defined between said cap and said neck.

The present invention also relates to an assembly comprising a fluid reservoir, particularly for a motor vehicle, and a cap,

said reservoir comprising a neck equipped with a screw thread,

said cap comprising a screwing cover comprising a screw thread, and a safety cell configured to allow the passage of gas from the interior to the exterior of the reservoir, and/or vice versa, when the cap is screwed onto said neck and when a pressure difference between the interior and the exterior of the reservoir is greater or less than at least one predetermined threshold value,

characterized in that said safety cell comprises an annular seal which is configured to seal against an annular wall of said neck when the cap is screwed onto the neck using said screw threads, and which is further configured to collaborate with this annular wall by simply bearing with elastic deformation in order to provide a stable transport position for said assembly in which the cap is premounted on the neck and said screw threads are not yet cooperating with one another.

The assembly according to the invention may comprise one or more of the following features, considered in isolation from one another or in combination with one another:

-   -   said annular seal is housed in an outer annular groove of said         cell,     -   said annular seal is housed in an outer annular groove of a         substantially cylindrical body of said cell, which is intended         to be surrounded by said annular wall,     -   said neck is of the coaxial double-walled type and comprises an         outer annular wall bearing said screw thread and an inner         annular wall configured to cooperate with said seal,     -   the inner annular wall at its upper end has a free annular edge         which is crenellated and exhibits an alternation of solid parts         and of recessed parts which define spaces for the passage of gas         in the radial direction,     -   said seal bears radially against said free annular edge when the         cap is in the aforementioned stable transport position,     -   said seal bears radially against said free annular edge when the         cap is in the aforementioned stable transport position,     -   said annular wall comprises at least two, and preferably at         least three, portions of different inner diameters, which are         each able to cooperate with said annular seal,     -   the free annular edge comprises a first portion of inner         diameter H1 and the rest of the inner annular wall comprises         another portion of inner diameter H3 which is less than H1,     -   the free annular edge comprises a second portion of inner         diameter H2, between said first and other portions, where H2 is         comprised between H3 and H1.

The invention also relates to a motor vehicle comprising at least a cap, a reservoir or an assembly as described hereinabove.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and further details, features and advantages of the present invention will become more clearly apparent from reading the following description given by way of nonlimiting example and with reference to the attached drawings in which:

FIG. 1 is a schematic perspective view of a motor vehicle reservoir equipped with a cap according to the invention,

FIG. 2 is a schematic exploded perspective view of the reservoir and of the cap of FIG. 1,

FIGS. 3a to 3c are schematic perspective views of a ring of the cap of FIG. 1,

FIG. 4 is a schematic perspective view of the cover of the cap of FIG. 1,

FIGS. 5a to 5c are schematic partial perspective views of the reservoir of FIG. 1,

FIG. 6 is a schematic partial perspective view on a larger scale of a detail of the reservoir and of the cap of FIG. 1,

FIGS. 7a and 7b are schematic perspective views of a safety cell of the cap of FIG. 1,

FIG. 8 is a schematic partial view in cross section of the reservoir and of the cap of FIG. 1, the cap being fixed to a neck of the reservoir,

FIGS. 9 and 10 are schematic partial views, in perspective and in section respectively, of the reservoir and of the cap of FIG. 1, the cap being premounted on the neck of the reservoir,

FIG. 11 is a schematic perspective view of a motor vehicle reservoir equipped with a cap according to the invention,

FIG. 12 is a schematic partial view in section of the reservoir and of the cap of FIG. 11,

FIG. 13 is a schematic perspective view of the cover of the cap of FIG. 11,

FIGS. 14 and 15 are schematic perspective views of a ring of the cap of FIG. 11,

FIG. 16 is a schematic partial perspective view of the reservoir of FIG. 11,

FIG. 17 is another schematic view in section and in perspective of the reservoir and of the cap of FIG. 11,

FIG. 18a is a schematic view in section of the reservoir and of the cap of FIG. 21, on A-A, the cap being in a position in which it is premounted on the neck of the reservoir,

FIG. 18b is a schematic partial view in section of the reservoir and of the cap of FIG. 21, on B-B, the cap being in the premounted position,

FIGS. 19a and 19b are schematic view similar to those of FIGS. 18a and 18b and showing the cap in a position at the start of screwing onto the neck of the reservoir,

FIGS. 20a and 20b are schematic views similar to those of FIGS. 18a and 18b and showing the cap in a position at the end of screwing onto the neck of the reservoir,

FIG. 21 is a view from above of a reservoir and of a cap according to another alternative form of embodiment of the invention,

FIG. 22 is a schematic perspective view in section of the neck of the reservoir of FIG. 21,

FIG. 23 is a schematic view in section on a larger scale of the neck of the reservoir of FIG. 21,

FIG. 24 is a schematic view in section of a safety cell of the cap of FIG. 21, and

FIG. 25 is a schematic perspective view of a cover of the cap of FIG. 21.

DETAILED DESCRIPTION

FIGS. 1 to 10 depict one embodiment of the cap 10 according to the invention, which is attached and fixed to a neck 12 of a fluid reservoir such as an expansion vessel of a motor vehicle.

As can be seen in FIG. 2, the cap 10 essentially comprises three elements, namely a cover 16, a safety cell or valve 18, and a ring 20.

FIGS. 3a to 3c show the ring 20 in isolation. FIG. 4 shows the cover 16 in isolation. FIGS. 5a to 5c show the reservoir 14 on its own, and FIGS. 7a and 7b show the safety cell 18. The other FIGS. 1, 6, 8, 9 and 10 show the cap 10 fixed or premounted on the neck 12 of the reservoir 14.

The ring 20 has an axis A of revolution. Overall, it comprises two axial end parts, these respectively being an upper end part 20 a and a lower one 20 b. Its upper part 20 a has an outer diameter smaller than that of its lower part 20 b. The upper part 20 a comprises a screw thread 22, in this instance an external screw thread, for screwing the cover 16 on. The lower part 20 b, of cylindrical overall shape, is connected to the upper part 20 a by an annular shoulder 24 defining an annular surface substantially perpendicular to the axis A.

The upper part 20 a comprises a substantially cylindrical inner annular surface 20 aa, of diameter D1. Ribs 26 projecting from the surface 20 aa are uniformly distributed about the axis A. The ribs 26 are substantially rectilinear and in this instance extend substantially parallel to the axis A. The radially outer ends of the ribs 26 are situated at the level of the surface 20 aa and therefore of the diameter D1, and their free, radially inner ends are situated on a circumference centered on the axis A, of diameter D2 (naturally smaller than D1).

The lower part 20 b comprises an annular row of slots 28 passing through in the radial direction. The slots 28 are uniformly distributed about the axis A. In this instance there are three of them. They each have a rectilinear overall shape and extend substantially in one and the same transverse plane, namely perpendicular to the axis A.

The lower part 20 b comprises a sectorized inner annular rim 30 made up of sectors 30 a, in this instance three of them, uniformly distributed about the axis A.

The sectors 30 a are aligned in the axial direction with the slots 28 and have substantially the same circumferential spreads. In the example depicted, each slot 28 and each sector 30 a extends about the axis A over an angle of approximately 20-40°.

The slots 28 are situated in the immediate vicinity of the sectors 30 a and here extend just above them. The slots are configured to give the sectors 30 a certain degree of flexibility and thus allow the sectors small amounts of elastic deformation, which are particularly useful in elastically snap-fastening the ring 20 onto the neck 12, as will be described in greater detail in what follows.

For that, the sectors 30 a bear elastic snap-fastening means which here take the form of ramps 32. Each sector 30 a bears, on its upper surface, which here is aligned with or coincident with a lower surface of the corresponding slot 28, a projecting ramp 32. Each ramp 32 comprises an incline 32 a oriented in the circumferential direction, and an end stop 32 b oriented in the axial direction. The inclines 32 a are oriented according to the direction of the screw thread so that they can cooperate by sliding with the neck 12, until the ramps 32 elastically snap fasten into complementarily shaped recesses of the neck. The end stops 32 b can then, in this position, cooperate with the neck to prevent accidental removal of the ring from the neck of the reservoir.

The cover 16 of FIG. 4 is intended to cover and close the neck 12 of the reservoir 14. It has an annular overall shape with an axis of revolution B which is intended to coincide with the axis A when the cap is being mounted on the neck.

It comprises an upper wall 16 a of circular and flat overall shape and the external periphery of which is connected to a substantially cylindrical wall 16 b. This cylindrical wall 16 b comprises an inner screw thread 16 ba that complements the screw thread of the ring 20. The wall 16 b additionally comprises an outer surface 16 bb configured to make it easier for a user to grasp for the purposes of screwing/unscrewing the cover.

The cylindrical wall 16 b comprises, on its lower free annular edge, a notch 34 oriented substantially in a radial direction. This notch forms elastic snap-fastening means which are intended to cooperate with a stud 36 of complementary shape visible in FIG. 3a . This stud 36 projects from the transverse surface 24 of the shoulder. It will thus be appreciated that, when the cover 16 is screwed onto the ring 20, the cover is intended to be screwed on until the stud 36 by elastic snap-fastening enters the notch 34 of the cover. That makes it possible to define in a positive way an end-of-travel position for the screwing of the cover onto the ring and thus alerts the user to the fact that the cover has been correctly screwed onto the ring.

As can be seen in FIG. 8 which illustrates the position in which the cover 16 is screwed onto the ring 20, the free lower edge of the cover may be spaced by an axial clearance away from the transverse surface 24 of the shoulder (even through the stud 36 is engaged in the notch 34) and the outer periphery of the wall 16 a of the cover 16 may bear axially against the upper edge of the ring. It may also be seen from this figure that the outer periphery of the wall 16 a comprises an inner annular groove 38 for housing the outer periphery of a split ring 40, which is also visible in FIGS. 2, 7 a and 7 b. The inner periphery of this split ring 40 is engaged in an outer annular groove of the safety cell 18, which is therefore fixed to the cover 16 by the split ring 40.

The neck 12 of the reservoir 14 defines an opening 42, in this instance circular, for filling the reservoir and for emptying fluid from the reservoir. The neck 12 comprises a cylindrical wall 44 defining the opening 42 and has an axis of revolution C which is intended to coincide with the axes A and B in the position in which the cap is mounted on the neck.

The cylindrical wall 44 and, in particular, the outer annular surface 44 a thereof, has an external diameter D3 which is equal to or slightly smaller than the diameter D2. The wall 44 at its upper end has a free annular edge 46 which is crenellated and exhibits an alternation of solid parts 46 a and of recessed parts 46 b, evenly distributed about the axis C. The recessed parts 46 b define spaces for the passage of gas in the radial direction. As an alternative, in place of the crenellations of the edge 46, the latter may comprise radial through-orifices.

The wall 44 at its lower end comprises a radial additional thickness 48 which defines around the wall 44 an annular shoulder having a transverse upper annular surface 48 a. A sectorized outer annular rim 50 is situated at the outer periphery of the additional thickness 48 and comprises sectors 50 a that complement the sectors 30 a of the ring 20 so as to create means of fastening by bayonet effect.

The sectors 50 a, of which there are three here, are uniformly distributed about the axis C. They have substantially the same circumferential spread. In the example depicted, each sector 50 a extends about the axis A over an angle of approximately 80-100°.

The sectors 50 a bear means of elastic snap-fastening that complement the ramps 32. Here they take the form of recesses 52 of a shape that complements that of the ramps 32. Each sector 50 a on its lower surface bears a recess 52. Each recess 52 comprises an incline 52 a oriented in the circumferential direction, and an end stop 52 b oriented in the axial direction. The inclines 52 a are oriented according to the direction of the aforementioned screw thread so that they are substantially parallel to the inclines 32 of the ramps in the mounted position (cf. FIG. 6). The end stops 52 b are then able in this position to cooperate by circumferential bearing with the end stops 32 b of the ring to prevent accidental removal of the ring from the neck of the reservoir.

The reservoir 14 is equipped with a gas duct 54 which may be formed as one piece with this reservoir 14. The duct 54 here has a rectilinear overall orientation and runs substantially parallel to the axis C. It preferably extends over the entire height of the reservoir and opens at its upper end onto the surface 48 a of the shoulder and thus forms an orifice 56, and at its lower end into the bottom of the reservoir (not depicted). The passage cross section of the duct in this instance is shaped as an arc of a circle about the axis C. That allows the orifice 56, situated at the immediate periphery of the cylindrical wall 44, to hug the shape of this wall. The orifice 56 thus comprises an inner annular edge situated on a circumference of diameter D3, and additionally comprises an outer annular edge situated on a circumference of diameter D4, this diameter D4 preferably being substantially equal to the diameter D1, as can be seen in FIG. 8.

This FIG. 8 reveals that the ring 16 defines, around the neck, an annular space 58 which is sectorized because of the presence of the ribs 26. The ribs 26 can cooperate by sliding at the time of mounting with the wall 44 and bearing radially on this wall, in order to maintain a radial clearance between the ring 16 and the neck 12 and thus define this space 58. This space 58 is aligned with and in fluidic communication with the orifice 56 and the duct 54. Furthermore, the spaces 60 defined by the recessed parts 46 b of the neck are also in fluidic communication with the space 58. This is rendered possible for example by dimensioning the height or axial dimension of the recessed parts 46 b so that they communicate with the space 58.

As an alternative, in place of all or part of the duct 54, the reservoir 14 may comprise an orifice 62 formed in the additional thickness 48 and intended to provide fluidic communication between the space 58 (or part of the duct 56 formed in the additional thickness 48) and the outside of the reservoir 14. This orifice 62 is indicated schematically in dotted line in FIG. 8. It opens laterally under the rim 50.

FIGS. 7a, 7b and 8 illustrate one example of a safety cell 18 which is a nonlimiting example. This cell 18 comprises a hollow body 64 having an axis D of revolution likewise intended to coincide with the axes A, B and C in the mounted position.

A first valve shutter 66 formed by an annulus is mounted in the body 64 and extends about the axis D. A first helical compression spring 68 is mounted around the axis D and bears at its upper end against an upper wall of the body and at its lower end against the valve shutter 66.

A second valve shutter 70 is mounted in the body 64 and is centered on the axis D. A second helical compression spring 72 is mounted around the axis D and at its lower end bears against the lower wall of the body and at its upper end bears against the valve shutter 70. The valve shutter 66 surrounds the valve shutter 70 and bears axially upon the latter.

An annular seal, in this instance an O-ring seal, 74, surrounds the body 64 of the cell 18 and is mounted in an outer annular groove of the body 64. This seal 74 is elastically deformable. In the unstressed free position its external diameter is greater than the external diameter of the body of the cell or of the portion of the body of the cell that is intended to be engaged in the neck 12 of the container. The outside diameter of the seal 74 is also greater than the inside diameter of the wall 44 of the neck. This is advantageous for allowing the cap to be premounted on the neck of the reservoir, as can be seen in FIGS. 9 and 10.

The assembly formed by the reservoir 14 and the cap 10 can be delivered to a motor manufacturer in this premounted position in which the cap is simply engaged by axial translation in the neck 12, until its seal 74 is bearing radially against the internal surface of the wall 44. Mere direct cooperation between the seal 74 and this wall 44 is enough to hold the cap in this position. All that an operator needs then to do is to remove the cap, simply by withdrawing it axially, in order to proceed with filling the reservoir. In the premounted position, the sectors 32 a of the ring can be aligned axially with the circumferential spaces extending between the sectors 52 a of the neck 12 (FIG. 9).

In order to completely secure the cap 10 on the neck 12, the sectors 32 a of the ring need to be axially aligned with the circumferential spaces extending between the sectors 52 a of the neck 12, the ring needs to be moved translationally until the sectors 32 a pass through these circumferential spaces and become positioned underneath them, then the ring needs to be rotated about the axes A-D until the sectors 32 a are situated underneath the sectors 52 a and until the ramps 32 are housed by elastic snap-fastening in the recesses 52. As the ring is turned, the ramps 32 cooperate by sliding with the sectors 52 a, and this may lead to elastic deformation of the sectors 32 a.

When the cap is being fitted, the entire cap can be attached and fixed at the same time. Thus, the ring 20 equipped with the cover 16 and with the cell 18 can be moved and fitted by an operator, as mentioned in the foregoing.

The cap in this exemplary embodiment affords a solution to a number of disadvantages of the earlier technology:

-   -   the cap is mounted on the reservoir by bayonet-fastening as far         as a locking point; thereafter, the cover can be unscrewed from         the ring in order to fill the reservoir;     -   the cap can be fixed temporarily to the reservoir to simplify         assembly; it is premounted on the neck (not locked),         additionally affording the reservoir protection against         potential contamination and knocks on the sealing zones;     -   the ring, once mounted on the reservoir, defines a space on the         outside of the neck, which communicates via the crenellations or         holes with the inside of the neck above the cap seal; this space         then communicates with at least one orifice or a duct of the         reservoir in order to allow the gases to be ducted out of the         reservoir, toward the bottom or toward the side of the         reservoir; it is the saving made on the manufacturer's assembly         lines that makes this solution competitive because it could now         be performed by assembly on the reservoir prior to delivery.

FIGS. 11 to 17 depict an alternative form of embodiment of the cap 110 according to the invention, which is attached and fixed to a neck 112 of a fluid reservoir 114 such as a motor vehicle expansion vessel.

The cap 110 essentially comprises three elements, namely a cover 116, a safety cell or valve 118 and a ring 120.

FIGS. 14 and 15 show the ring 120 in isolation. FIG. 13 shows the cover 116 in isolation. FIG. 16 shows the reservoir 114 on its own. The other figures show the cap 110 fixed to the neck 112 of the reservoir 114, FIGS. 12 and 17 showing the safety cell 118.

The ring 120 has an axis A of revolution. It comprises a screw thread 122, in this instance an external screw thread, for screwing on the cover 116. It comprises a substantially cylindrical inner annular surface 120 aa, of diameter D1. Ribs 126 projecting from the surface 120 aa are uniformly distributed about the axis A. The ribs 126 are substantially rectilinear and in this instance extend substantially parallel to the axis A. The radially outer ends of the ribs 126 are situated at the surface 120 aa and therefore at the diameter D1, and their radially inner ends are joined together by ring sectors 127 and situated on a circumference centered on the axis A, of diameter D2 (which is naturally smaller than D1).

Means of guidance and sliding and elastic snap-fastening are also arranged on the surface 120 aa. In the example depicted, the guidance and sliding means comprise slideways 128 in this instance projecting from the surface 120 aa. There are four of these slideways 128 uniformly distributed about the axis A. The slideways 128 are of two types, a first type of slideway 128 a comprising a single radial wall and a second type of slideway 128 b comprising two radial walls spaced circumferentially apart by a predetermined distance. The slideways 128 a are diametrically opposed, as too are the slideways 128 b.

The slideways 128 a and their walls run parallel to the axis A. They have their upper ends situated at the level of the upper end of the surface 120 aa of the ring, and their lower ends bearing elastic snap-fastening means. These elastic snap-fastening means in this instance are catching teeth 129.

The slideways 128 b and their walls run parallel to the axis A. They have their upper ends situated at the level of the upper end of the surface 120 aa of the ring, and their lower ends connected to ring sectors 127 in the example depicted. The slideways 128 define a longitudinal housing 131 parallel to the axis A and extending over the entire height or axial dimension of the ring 120.

The cover 116 of FIG. 13 is intended to cover and closed the neck 112 of the reservoir 114. It has an annular overall shape and has an axis of revolution B which is intended to coincide with the axis A when the cap is mounted on the neck.

It comprises an upper wall 116 a of flat and circular overall shape and the external periphery of which is connected to a substantially cylindrical wall 116 b. This cylindrical wall 116 b comprises an internal screw thread 116 ba that complements the screw thread of the ring 120. The wall 116 b further comprises an outer surface 116 bb configured to make it easier for a user to grasp, so that the cover can be screwed on/unscrewed.

As can be seen in FIGS. 11, 12 and 17 which illustrate the position in which the cover 116 is screwed onto the ring 120, the free lower edge of the cover may bear axially against the upper surface 148 a of the shoulder of the neck.

It may also be seen in FIG. 12 that the outer periphery of the wall 116 a comprises an inner annular groove 138 for housing the outer periphery of a split ring 140. The inner periphery of this split ring 140 is engaged in an outer annular groove of the safety cell 118, which is therefore fixed to the cover 116 via the split ring 140.

The neck 112 of the reservoir 114 defines an opening 142, in this instance circular, for filling the reservoir and for removing fluid from the reservoir. The neck 112 comprises a cylindrical wall 144 defining the opening 142 and has an axis of revolution C, which is intended to coincide with the axes A and B when the cap is in the position mounted on the neck.

The cylindrical wall 144 and, in particular, the outer annular surface 144 a thereof has an outside diameter D3 which is equal to or slightly smaller than the diameter D2. The wall 144 at its upper end has a free annular edge 146 which is crenellated and exhibits an alternation of solid parts 146 a and of recessed parts 146 b uniformly distributed about the axis C. The recessed parts 146 b define spaces for the passage of gas in the radial direction. As an alternative, in place of the crenellations of the edge 146, this edge could comprise radial through-orifices.

The wall 144 at its lower end comprises a radial additional thickness 148 which defines around the wall 144 an annular shoulder exhibiting a transverse upper annular surface 148 a.

The neck 112 comprises means of guidance and sliding and elastic snap-fastening on the wall 144. In the example depicted, the guiding and sliding means comprise rails 149, in this instance projecting from the outer surface of the wall 144. There are four rails 149 uniformly distributed about the axis C. They are intended to cooperate with the slideways 128. Each rail comprises a single radial wall.

The rails 149 and their walls run parallel to the axis C. In the example depicted, they are situated so they project from the solid parts 146 a. They have their upper ends situated at the level of the upper ends of the solid parts 146 a and their lower ends situated at the level of the shoulder of the neck.

Two of the rails, which are diametrically opposed, each comprise an elastic snap-fastening notch 150 intended to collaborate with one of the catching teeth 129.

The reservoir 114 is equipped with a gas duct 154 which may be formed as one piece with this reservoir 114. The duct 154 here has a rectilinear overall orientation and runs substantially parallel to the axis C. It preferably extends over the entire height of the reservoir and opens at its upper end onto the surface 148 a of the shoulder and thus forms an orifice 156, and at its lower end into the bottom of the reservoir (not depicted). The passage cross section of the duct here is an arc of a circle about the axis C. That allows the orifice 156 situated at the immediate periphery of the cylindrical wall 144 to conform to the shape of this wall. The orifice 156 thus comprises an inner annular edge situated on the circumference of diameter D3 and also comprises an outer annular edge situated on a circumference of diameter D4, this diameter D4 preferably being substantially equal to the diameter D1.

The ring 116 defines around the neck an annular space 158 which is sectorized by the presence of the ribs 126, of the rails 149 and of the slideways 128. The sectors 127 may cooperate by sliding during mounting with the wall 144 and by bearing radially on this wall, in order to maintain a radial clearance between the ring 116 and the neck 112 and thus define this space 158. The rails 149 also cooperate by engagement and axial sliding with the housings 131. The space 158 is aligned and in fluidic communication with the orifice 156 and the duct 154. Moreover, the spaces 160 defined by the recessed parts 146 b of the neck are also in fluidic communication with the space 158. This for example is rendered possible by dimensioning the height or axial dimension of the recessed parts 146 b in such a way that they communicate with the space 158 (FIG. 17).

The safety cell 118 may be similar to the one 18 described in the foregoing.

The assembly formed by the reservoir 114 and the cap 110 can be delivered to a motor manufacturer in a premounted position as mentioned hereinabove.

In order to fix the cap 110 on the neck 112 the rails 149 need to be axially aligned with the longitudinal housings 131 of the ring 120 and the ring needs to be moved translationally until the teeth 129 of the slideways 128 a elastically snap-fasten to the notches 150 of the rails 149.

During the fixing of the cap, the entire cap can be attached and fixed at the same time. Thus, the ring 120 equipped with the cover 116 and with the cell 118 can be moved and fixed by an operator as mentioned in the foregoing.

FIGS. 18a to 25 illustrate another alternative form of embodiment of the invention, illustrating in greater detail the ability to premount the cap on the neck of the reservoir.

The references used in these figures reflect those used in the foregoing in as much as they refer to features already described.

In this alternative form of embodiment, the ring 220 bearing the external screw thread 222 is formed as a single piece with the neck 112. The neck 112 is of the double-skinned or double-walled type and comprises two coaxial annular walls, these respectively being an inner and an outer wall. The outer wall is formed by the ring 220 and is substantially cylindrical. The inner wall 144 at its upper end comprises the crenellated annular edge 146 described in the foregoing.

As can be seen in FIGS. 22 and 23 in particular, the annular wall 144 comprises at least two, and preferably at least three, portions of different internal diameters, each of which are able to cooperate with the annular seal 174 of the safety cell 118. In the example depicted, the free annular edge 146 comprises a first portion 146 aa, in this instance an upper portion, of internal diameter H1, and a second portion 146 ab, in this instance an intermediate portion, of internal diameter H2 smaller than H1. The rest of the wall 144 comprises a third portion 146 ac, in this instance a lower portion, of internal diameter H3 which is smaller than H1 and H2. The portions 146 aa, 146 ab, 146 ac are connected to one another by connecting ramps R1, R2. For information, FIG. 16 illustrates an alternative form having two portions with different internal diameters as opposed to three in the example of FIG. 18a et seq.

As mentioned in the foregoing, the annular seal 174 of the safety cell is configured to cooperate by simply bearing with elastic deformation on the annular wall 144 in order to provide a stable transport position in which the cap is premounted on the neck and the screw threads 116 ba, 222 are not yet cooperating with one another, as is visible in FIGS. 18a and 18 b.

In this position, the seal 174 is elastically deformed by bearing radially on the portion 146 aa or 146 ab of the wall 144. The screw threads may bear axially against one another in this position, as can be seen in the zone U of FIG. 18 a.

FIGS. 19a and 19b depict an intermediate screwing step in which the seal 174 is bearing radially against the portion 146 ab or the ramp R2 connecting this portion to the portion 146 ac. FIGS. 20a and 20b depict a final screwing step in which the seal 174 is bearing radially against the smallest-diameter portion 146 ac, namely under the edge 146. In this position, the cap 110 is bearing axially against the shoulder of the neck of the reservoir.

The assembly formed by the reservoir 114 and the cap 110 can be delivered to a motor manufacturer in the premounted position of FIGS. 18a and 18b . All an operator then has to do is to remove the cap by axial translation in order to proceed to fill the tank via its neck. The cap can then be screwed and tightened onto the neck. 

1. An assembly comprising: a fluid reservoir (14, 114), for a motor vehicle, and a cap (10, 110), said reservoir comprising a neck (12, 112) equipped with a screw thread (22, 122, 222), said cap comprising a screwing cover (16, 116) comprising a screw thread (16 ba, 116 ba), and a safety cell (18, 118) configured to allow the passage of gas between an interior of the reservoir and an exterior of the reservoir, when the cap is screwed onto said neck and when a pressure difference between the interior and the exterior of the reservoir is greater or less than at least one predetermined threshold value, wherein said safety cell comprises an annular seal (74, 174) which is configured to seal against an annular wall (44, 144) of said neck when the cap is screwed onto the neck by cooperation of the screw thread of said neck and the screw thread of the cover, and which annular seal is further configured to collaborate with the annular wall by bearing with elastic deformation in order to provide a stable transport position for said assembly in which the cap is premounted on the neck and the screw thread of said neck and the screw thread of the cover are not yet cooperating with one another.
 2. The assembly as claimed in claim 1, in which said annular seal (74, 174) is housed in an outer annular groove of said cell (18, 118).
 3. The assembly as claimed in claim 1, in which said annular seal (74, 174) is housed in an outer annular groove of a substantially cylindrical body (64) of said cell, which is intended to be surrounded by said annular wall (44, 144).
 4. The assembly as claimed in claim 1, in which said neck (12, 112) is of the coaxial double-walled type and comprises an outer annular wall bearing said screw thread of said neck (22, 122, 222) and the annular wall (44, 144) configured to cooperate with said seal (74, 174) is an inner annular wall of said neck.
 5. The assembly as claimed in claim 4, in which the annular wall (44, 144) at its upper end has a free annular edge (46, 146) which is crenellated and exhibits an alternation of solid parts (46 a, 146 a) and of recessed parts (46 b, 146 b) which define spaces for the passage of gas in a radial direction.
 6. The assembly as claimed in claim 5, in which said seal (74, 174) bears radially against said free annular edge (46, 146) when the cap (10, 110) is in the stable transport position.
 7. (canceled)
 8. The assembly as claimed in claim 6, in which said annular wall comprises at least two portions (146 aa, 146 ab, 146 ac) of different inner diameters, which are each able to cooperate with said annular seal (74, 174).
 9. The assembly as claimed in claim 8, in which the free annular edge (146) comprises a first portion (146 aa) of inner diameter H1 and the rest of the inner annular wall (144) comprises another portion of inner diameter H3 which is less than H1.
 10. The assembly as claimed in claim 9, in which the free annular edge (146) comprises a second portion (146 ab) of inner diameter H2, between said first and other portions, where H2 is comprised between H3 and H1.
 11. A safety cap (10, 110) for a fluid reservoir (14, 114) of a motor vehicle, said cap being configured to be attached and fixed to a neck (12, 112) of said reservoir, said cap comprising: a screwing cover (16, 116) comprising a first screw thread (16 ba, 116 ba), and a safety cell (18, 118) configured to allow the passage of gas between an interior of the reservoir and an exterior of the reservoir, when the cap is fixed to said neck and when a pressure difference between the interior and the exterior of the reservoir is greater or less than at least one predetermined threshold value, wherein the cap further comprises: a ring (20, 120) comprising means (30, 30 a, 32, 128, 129) for fixing to said neck and a second screw thread (22, 122) configured to cooperate with said first screw thread, said cell being at least partly housed in the neck and surrounded by said cover and/or said ring when the cap is fixed on said neck, wherein said ring (20, 120) comprises an inner annular surface (20 aa, 120 aa) intended to surround, with clearance, an outer annular surface (44 a, 144 a) of said neck (12, 112) so as to define a space (58, 158) for the passage of gas between the ring and the neck.
 12. The cap (10, 110) as claimed in claim 1, in which said ring (20, 120) comprises ribs (26, 126) projecting from said inner annular surface (20 aa, 120 aa) and able to cooperate by bearing and/or sliding with said outer annular surface (44 a, 144 a) of said neck (12, 112).
 13. The cap (10, 110) as claimed in claim 12, in which said ring (20, 120) comprises means (30, 30 a, 32, 128, 129) for fixing to said neck (12, 112) by bayonet effect and/or elastic snap-fastening.
 14. The cap (10) as claimed in claim 13, in which said ring (20) comprises inner annular rim sectors (30 a) which are intended to cooperate by bayonet effect with outer annular rim sectors (50 a) of said neck (12).
 15. The cap (10) as claimed in claim 14, in which said inner annular rim sectors (30 a) of said ring (20) bear first elastic snap-fastening means (32) intended to cooperate with complementary elastic snap-fastening means (52) of said outer annular rim sectors (50 a) of said neck (12).
 16. The cap (10) as claimed in claim 15, in which said ring (20) comprises circumferential through-slots (28) extending along and in proximity to said inner annular rim sectors (30 a) so as to provide them with a certain degree of flexibility.
 17. The cap (110) as claimed in claim 13, in which said ring (120) comprises slideways (128) configured to cooperate with rails (149) of said neck (112) in order to produce guiding by axial sliding when mounting said ring on said neck.
 18. The cap (110) as claimed in claim 17, in which at least one of said slideways (128) bears first elastic snap-fastening means (129) intended to cooperate with complementary elastic snap-fastening means (150) of at least one of said rails (149).
 19. A fluid reservoir (14, 114) for a motor vehicle, said reservoir comprising: a neck (12, 112) on which there is intended to be attached and fixed a cap (10, 110), wherein said neck comprises either: (a) a cylindrical wall (44) comprising outer annular rim sectors (50 a), said outer annular rim sectors (50 a) of said cylindrical wall (44) bear elastic snap-fastening means (52 a), or (b) a cylindrical wall (144) and an annular row of rails (149) projecting from an outer cylindrical surface of this cylindrical wall, said rails being substantially parallel to one another and to an axis (C) of revolution of this cylindrical wall, wherein at least some of said rails (149) bear elastic snap-fastening means (150). 20-23. (canceled)
 24. The reservoir (14, 114) as claimed in claim 19, in which said cylindrical wall (44, 144) comprises a crenellated free annular edge (46, 146) comprising solid parts (46 a, 146 a) alternating with recessed parts (46 b, 146 b) for the passage of gas.
 25. The reservoir (14, 114) as claimed in claim 24, in which said neck (12, 112) comprises an annular shoulder for the axial bearing of said cap (10, 110) and onto which a gas passage orifice (56, 156) can open.
 26. The reservoir (14, 114) as claimed in claim 25, comprising a gas passage duct (54, 154) defining said orifice (56, 156) and extending substantially over the height of said reservoir. 27-29. (canceled)
 30. An assembly, comprising: a reservoir (14, 114) and a cap (10, 110); wherein the reservoir includes a neck (12, 112) with an outer annular surface (44 a, 144 a); wherein the cap includes: a screwing cover (16, 116) comprising a first screw thread (16 ba, 116 ba), a safety cell (18, 118) configured to allow the passage of gas between an interior of the reservoir and an exterior of the reservoir, when the cap is fixed to said neck and when a pressure difference between the interior and the exterior of the reservoir is greater or less than at least one predetermined threshold value, a ring (20, 120) comprising means (30, 30 a, 32, 128, 129) for fixing to said neck and a second screw thread (22, 122) configured to cooperate with said first screw thread, wherein said safety cell is at least partly housed in the neck and surrounded by said cover and/or said ring when the cap is fixed on said neck, wherein said ring (20, 120) comprises an inner annular surface (20 aa, 120 aa) to surround, with clearance, the outer annular surface (44 a, 144 a) of said neck (12, 112) so as to define a space (58, 158) for the passage of gas between the ring and the neck; wherein the cap is either: premounted on said neck (12, 112), said cap being held on said neck only by the cooperation between an annular seal (74, 174) and a cylindrical wall (44, 144) of the neck, or fixed to said neck by bayonet effect and/or elastic snap-fastening.
 31. A motor vehicle, comprising at least one assembly as claimed in claim
 30. 